From /u/pipesBcallin

Raise Up Seed

[quoting]

The Book of Mormon identifies one reason for God to command polygamy: to increase the number of children born in the gospel covenant in order to “raise up seed unto [the Lord]” (Jacob 2:30). Funny enough on the church essay about plural marriage we find foot note #6 about 5 paragraphs down where they claim

https://www.churchofjesuschrist.org/topics/plural-marriage-and-families-in-early-utah?lang=eng#6

Plural marriage did result in the birth of large numbers of children within faithful Latter-day Saint homes.

but then point us to foot note #6 which says

Studies have shown that monogamous women bore more children per wife than did polygamous wives except the first. Fertility at the societal level, however, was enhanced because of the near universality of marriage among women and the abundant opportunities for remarriage among previously married women of childbearing age. L. L. Bean and G. P. Mineau, “The Polygyny–Fertility Hypothesis: A Re-evaluation,” Population Studies 40 (1986): 67–81; Miriam Koktvedgaard Zeitzen, Polygamy: A Cross Cultural Analysis (Oxford and New York: Berg, 2008), 62–63.

This foot note points to a couple of studies showing monogamous marriages as having more children. An example of this would be Brigham Young having 55 wives and only 57 children. Of those 55 wives it also states 29 of them were child-bearing wives. I am not sure why the others bore him no children but there could have been a large number of reasons. This puts us at 1.9655 children per child-bearing women and 1.03636 children per wife. While at the same time in U.S. history between the years of 1850 to 1890 we can see that the average household across the country had between 3 to 4 children.

https://editorialexpress.com/cgi-bin/conference/download.cgi?db_name=MWM2008&paper_id=57

https://www.infoplease.com/us/household-and-family-statistics/us-households-size-1790-2006

This information plus the fact that there were more men then women in Utah during this time period means that if they had not been practicing polygamy there more then likely would have been more children born on average. Using only the 29 child-bearing women there could have been 87 - 116 instead of 57 and if you take on the full number as these number were based on nation average with people who would have had the similar issue with bearing children as there could have been with Brigham’s other wives you would be at 165 - 220. True this is only based off of Brigham Young but it is shown that the average household in the country had more children with monogamist women. Even the church agrees to this on their essay even if they try to hide it.

Mormonthink asks the question

So what is it: “Plural marriage did result in an increased number of children born to believing parents” or “Studies have shown that monogamous women bore more children per wife than did polygamous wives except the first.”

http://www.mormonthink.com/joseph-smith-polygamy.htm

I know there are a lot of reasons the church and it’s members give to explain why polygamy was necessary but the only reason that was called out for to have God command polygamy even if you want it interpreted that way as I don’t agree with this interpretation is in Jacob 2 : 30 as stated above.

30 For if I will, saith the Lord of Hosts, raise up seed unto me, I will command my people; otherwise they shall hearken unto these things.

This is repeated in D&C 132 : 63 using slightly different wording

63 But if one or either of the ten virgins, after she is espoused, shall be with another man, she has committed adultery, and shall be destroyed; for they are given unto him to multiply and replenish the earth, according to my commandment, and to fulfil the promise which was given by my Father before the foundation of the world, and for their exaltation in the eternal worlds, that they may bear the souls of men; for herein is the work of my Father continued, that he may be glorified.

Now my opinion on the matter is from this data I can only come to 2 conclusions

  1. This practice did not come from an all knowing God
  2. Or God did not know that his own commandment did not work for the reason he wanted it to.